The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a fine pattern in a semiconductor device.
Amorphous carbon has been used as a part of a hard mask stack structure, where the hard mask has been used in patterning an N-channel metal-oxide semiconductor field effect transistor (NMOSFET) device when forming a fine pattern of 100 nm or below. The amorphous carbon allows easier patterning, and shows better selectivity than typical capping or protective materials of a silicon oxide (SiO2) layer, silicon nitride (Si3N4) layer, and a silicon oxynitride (SiON) layer.
However, using amorphous carbon as a hard mask increases cost as compared to using a polysilicon layer as the hard mask, increasing the fabrication cost up to five to ten times. Furthermore, amorphous carbon shows deteriorated step coverage when formed over a peripheral region with large differences in heights, i.e., over various key boxes (align keys) used for monitoring photo and etch processes. Thus, a subsequent SiON layer may be formed unevenly. Consequently, when performing a rework process on a photoresist during a photo-exposure process, portions of the amorphous carbon may be lost, and undesired events (e.g., lifting and particle generation) may occur where the portions of the amorphous carbon are lost.